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Biomedical subjects

R H Helfant

Publications and source records attributed to R H Helfant.

At least 109 records · Page 6Linked to original sources
PubMed1979

Comparison of wall motion and regional ejection fraction at rest and during isometric exercise: concise communication.

The detection of regional abnormalities of left-ventricular wall motion provides strong evidence for the presence of coronary heart disease. In 129 patients undergoing coronary arteriography, the relative value of radionuclide angiographic assessment of wall motion was compared with computer-generated regional ejection fraction, at rest and during handgrip exercise. Wall motion was determined by superposition of computer-derived end-diastolic and end-systolic perimeters. Relative regional ejection fraction was determined using a computer-generated 16-color isocount image that permitted a quantitative assessment of zonal contribution to ejection fraction. Of the 129 patients, coronary arteries were normal in 31 and diseased in 98. Of 24 patients with single-vessel disease, wall-motion abnormalities were present, at rest or during exercise in 15, whereas regional ejection fraction detected 20 patients. Seventy-four patients had multivessel disease. Of these, wall-motion abnormalities occurred in 52 but regional ejection fraction was abnormal in 69 (p less than .01). Overall, sensitivity was 67% by wall motion and 91% by relative regional ejection fraction (p less than .001). Specificity was 94% by wall motion and 87% by regional ejection fraction (not significant). Thus, radionuclide angiographic assessment of regional ejection fraction during handgrip exercise is both highly sensitive and specific for coronary heart disease and significantly enhances detection of coronary heart disease compared with wall-motion assessment, with little loss in specificity.

Cardiac Output↗
PubMed1978

Ventriculographic-echocardiographic correlation in patients with asynergy.

The ability of echocardiography to detect segmental ventricular asynergy was evaluated in 41 patients before cardiac catheterization. Of 24 normal posterior wall segments by echocardiography, 23 were also normal by ventriculography, while one was hypokinetic. Of 17 asynergic posterior wall segments by echocardiography, 15 were asynergic and two were normal by ventriculography. Posterior wall excursion for the normal group was 1.30 +/- 0.18 cm (SD), while those demonstrating hypokinesis on ventriculography showed an excursion of 1.05 +/- 0.19 cm (P less than .005), and akinetic segments showed an excursion of 0.97 +/- 0.13 cm (P less than .005). In 15 patients, septal motion as determined by echocardiography was compared with the left anterior oblique ventriculogram. Of nine normal septal motions by echocardiography, seven were also normal by left anterior ventriculography (septal excursion, 0.84 +/- 0.25 cm). Of six patients with decreased echocardiographic septal motion, four were normal and two were abnormal by ventriculography. Although normal echocardiographic septal motion correlated well with ventriculography, decreased septal excursion by echocardiography did not.

Cardiac Catheterization↗
PubMed1978

Progressive transmural electrographic, myocardial potassium ion/sodium ion ratio and ultrastructural changes as a function of time after acute coronary occlusion.

The progressive transmural electrographic, biochemical and ultrastructural changes as a function of time after acute coronary occlusion were systematically assessed in eight dogs. Transmural plunge electrodes with poles 1 mm apart were placed in the ischemic and nonischemic zones, and coronary occlusion was maintained for 4 hours. Transmural full thickness biopsy specimens were obtained from each zone for electron microscopy before, and 1 and 4 hours after occlusion. Endocardial and epicardial layers were also obtained for assessment of myocardial potassium ion (K+) and sodium ion (Na+) concentrations. Before coronary occlusion, local Q waves were recorded an average depth of 1.0 +/- 0.34 mm from the endocardial surface. After 1 hour of occlusion, Q waves appeared at an average depth of 3.8 +/- 0.67 mm and progressed to a depth of 5.2 +/- 0.7 mm at 2 hours, 6.2 +/- 0.5 mm at 3 hours and 7.0 +/- 0.5 mm at 4 hours. After 1 hour, ultrastructural changes of early ischemia, including a decrease in glycogen and mild mitochondrial swelling, were seen in the endocardial layer; the epicardial layer showed normal morphologic features. After 4 hours, the endocardial layer showed well developed ischemic changes marked by the loss of mitochondrial cristae, vacuolization, the appearance of amorhopous mitochondrial cristae, vacuolization, the appearance of amorphous mitochondrial densities, an increase in interfibrillary space and the appearance of I bands. In contrast, the epicardial layer at this time showed only early ischemic changes. At the end of 4 hours, the endocardial layer showed a marked decrease in myocardial K+ concentration and an increase in Na+ concentration leading to complete reversal of K+/Na+ ratio (0.7 +/- 1.0; P less than 0.001). In the epicardial layer, a smaller decrease in K+ concentration and an increase in Na+ concentration occurred, resulting in a diminution but not a reversal of K+/Na+ ratio (1.4 +/- 0.2; P less than 0.005). Thus, the dynamic evolution of an acute myocardal infarction involves a sequential progression from endocardium to epicardium as a function of time, resulting in an epicardial "border zone" in the early stages after acute coronary occlusion.

Animals↗
PubMed1978

Effects of reperfusion on the regional contraction of ischemic and nonischemic myocardium following partial coronary obstruction.

In 14 dogs the effects on regional tension (Walton-Brodie gauges) and length (mercury-in-silastic) following 50% reduction (52.9 +/- 2.1) in coronary flow for two hours and reperfusion afterwards for one hour were addressed. Within five minutes of partial coronary occlusion, ejection tension in the ischemic zone decreased to 36.3 +/- 7.2% (P less than 0.001) and total tension to 64.4 +/- 5.7% of control (P less than 0.001) while phasic segment length increased to 165.2 +/- 16.3% control. No further significant changes in regional tension or length were observed throughout the two hour period of partial occlusion. Ejection tension remained positive and segment length maintained systolic shortening during the ejection phase throughout the period of occlusion. Following reperfusion, ejection tension in the ischemic zone increased from 35.1 +/- 5.9 to 87.0 +/- 22.0% (P less than 0.05) and total tension increased from 56.6 +/- 5.4 to 70.2 +/- 7.2% (P less than 0.02) while segment length decreased from 149.3 +/- 6.5 to 105.7 +/- 5.7% (P less than 0.001) within five to 15 min of reperfusion. The improvement in both regional tension development and segment length shortening was maintained throughout the one hour period of reperfusion. No significant changes were seen in the nonischemic zone. The present experimental study suggests that partial coronary occlusion producing a 50% reduction in coronary blood flow results in regional contractile changes. These changes are reversible at least twice as long as those following complete occlusion.

Animals↗
PubMed1977

Guanabenz and methyldopa on hypertension and cardiac performance.

In previous placebo-controlled studies, guanabenz was shown to be a safe and effective antihypertensive drug without acute effects on cardiac function. In view of its therapeutic advantages, a double-blind comparison of guanabenz with methyldopa was performed in a group of 36 patients over 6 mo. Both drugs produced statistically and clinically significant decreases in blood pressure with similar side effects. No laboratory or electrocardiographic abnormalities were found other than positive Coombs' tests which developed in 3 patients during methyldopa therapy. Cardiac performance in 26 of the patients, as measured by noninvasive techniques, showed no significant changes from either drug except for a progressive and statistically significant increase in systolic time interval (QS2) and the ratio of the pre-ejection period to left ventricular ejection time (PEP/LVET) during methyldopa therapy. For an additional 6 mo, continued efficacy and safety were shown under open conditions in those patients who had received guanabenz. The study suggests that guanabenz may be an important new antihypertensive drug because of effectiveness, absence of adverse cardiac effects, and paucity of side effects.

Adult↗